In recent years, considerable effort has been directed toward on-line web inspection to enhance the uniform quality of material webs, such as paper, glass, plastic, textiles, metallic sheets, fiberglass and sheet substrates. These web inspection assemblies are capable of high speed, high resolution detection and classification of surface imperfections in continuously manufactured products at rates in excess of 500 inches per second. Such surface imperfections include tears, through-holes, abrasions and scattering imperfections, impurities preventing local processing, stains and absorbing imperfections, pinch marks, thickness imperfections, and other far side and near side imperfections.
Web inspection assemblies often include an illumination source generating a point of light or a strip of light, and a photoelectric light sensor device or a conventional linear Charge Coupled Device (CCD) array or camera strategically positioned and angled to receive diffusely reflected light from a target surface illuminated by the generated light. Due to the scattering imperfections on or in the target surface, differences in light intensity of the reflected or transmitted light will be detected which may represent one of the above-mentioned surface imperfections. The light sensor device then delivers a signal to an electronic processing device representative of the type and magnitude of the surface imperfection.
To assure proper operation of the web inspection assembly, a visualization subsystem is often provided to format the scanner data generated by the sensor or camera device into visual form meaningful to the inspection operator. This verification tool is generally a visual image or topographic form illustrated on a display monitor.
Due to the high roll speeds of the moving web, real-time visualization of a detected anomaly is difficult to attain. Hence, the image of the defect is typically a freeze frame of the formatted scan data designated by the operator. Typically, these current visualization arrangements include real-time, remote visual inspection devices which require manual observation. Hence, these designs are relatively labor intensive to operate since the operator must devote their operative attention entirely to the viewing the monitor to identify a surface anomaly. This is true whether or not the moving web surface under inspection is good or defective. Should the operator fail to observe an anomaly on the display screen, for whatever reason, the defect may pass undetected.
Once an anomaly is visually and manually identified, some systems require the operator to manually pan or zoom in on the detected anomaly an define a region of interest to be displayed on the monitor. Subsequently, the operator must decide whether the processed image should be recorded in a storage device for retrieval at a later time. One problem associated with these systems is that the visualization techniques are performed in real-time scrolling illustrations on the monitor until a defect is identified. Subsequently, in some systems, the operator must pan or zoom in on the potential defect for viewing. During this operation, the operator must either stop or slow the moving web in order to view or mark the defect, or the operator must stop normal real-time viewing of the monitor while the web continues to move.
Stopping a high speed moving web, however, is a difficult task since the web is a continuous process manufacturing. Accordingly, the costs associated with stopping the web are substantial.
On the other hand, pausing the real-time scrolling to pan in on the defect may also be problematic since the web continues to move. Not only is this technique labor intensive, but should there be multiple defects when the operator is devoting his attention to viewing the first identified anomaly on the monitor, these other defects may pass through the visualization system undetected. Multiple tasking was not an option.
Further, visual resolution is often poor due in-part to the data compression techniques employed. To scale the entire cross-web to fit on the display monitor, the information must be reduced to the resolution of the monitor. In effect, the resolution is substantially reduced for viewing on a VGA monitor (typically 1024.times.768 pixels).
Finally, while some of these designs include storage devices to store records of the web inspection, the amount of storage space required to reproduce an image of a single defect is substantial since these designs are only capable of storing full frames. For example, even if a defect only measured 1.times.1 pixel, the full frames of 512.times.512 pixels would be stored in these designs. Accordingly, a substantial amount of unnecessary storage space is required, because each defect would require 262,144 bytes (i.e., 512.times.512).